Method of preparing a drying oil and intermediates therefor



United States Patent 8 Claims. (Cl. 260-4109) (Granted under Title 35, US. Code (1952), sec. 266) A nonexclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention pertains to methods of preparing certain drying oil-type coating materials from novel sources and to the preparation of certain novel compounds having utility as drying oils or as intermediates for the preparation ("if drying oil and other compounds.

This application is a division of application Serial No. 20,791, filed April 7, 1960.

In the course of an extensive investigation of the chemical compositions of the seeds of many less widely cultivated plants for unusual and potentially valuable constituents the availability of which could encourage extensive replacement planting in helpful partial substitution of major surplus crops, we have unexpectedly discovered that the principal constituent fatty acid (about 50-60 percent of the extractable fatty acid content) of the seed oil of the genus Dimorphotheca (represented by such species as D. aurantz'aca, commonly called the cape marigold, D. annua, D. calendulaceae, and D. sinuata) is the hitherto unknown acid, 9-hydroxy-trans,trans-10,12- octadecadienoic acid. Having isolated and characterized this acid, we hereby assign it the trivial name dimorphccolic acid. 40

We have also found that the glycerides obtained by petroleum ether extraction of Dimorphotheca oil are transesterified by refluxing the glyceride oil with methanol in the presence of sodium methoxide to give a mixture of fatty acid methyl esters of which mixture at least half consists of methyl dimorphecolate, which is separable in pure form, after acidification and ether extraction, by countercurrent distribution in an acetonitrile-hexane system.

We have further found that refluxing Dimorphotheca oil with glacial acetic acid, or with a 0.2 percent solution of p-toluenesulfonic acid in xylene, dehydrates the dimorphecolic acid moieties of the glycerides to form glycerides containing al1-trans-8,10,l2-octadecatrienoic acid to the extent of at least percent of the total fatty acid present. It is pointed out, however, that refluxing Dimorphotheca oil with xylene alone gives negligible yields of the triene while refluxing Dimorphotheca oil with xylene containing 2 percent rather than 0.2 percent of ptoluenesulfonic acid results in extensive polymerization 0 and port yields.

Refluxing Dimorphotheca oil with methanolic hydrochloric acid, on the other hand, simultaneously dehydrates the dimorphccolic acid moiety and trans-esterifies the glycerides to the methyl esters, thus forming a mixture of methyl esters comprising as a major portion the methyl ester of all-trans-S,10,12-octadecatrienoic acid, which can be isolated, for example, by countercurrent distribution in an acetonitrile-hexane system.

Films cast from a paint thinner solution of glacial acetic acid-dehydrated Dimorphotheca oil, at least half the fatty "ice acid content of which treated oil consists of all-trans-S, 10,12-octadecatrienoic acid, and also containing a standard lead naphthenate, cobalt naphthenate, mangenese naphthenate drier (0.501 g. of the drying oil dissolved in 1 ml. of paint thinner containing 0.006 g./n1l. of mixed metal naphthenates) proved superior in film-drying time even to films cast from a tung oil composition, as shown in Table I.

TABLE I Hours to Hours to Oil be tacky set to touch 1 Dimorphotheca 1% 78 H OAc-dehydrated Dimorphotheca V Tuna l Linseed 2 3 1 Films aged 2 to 6 days achieved a degree of hardness which would be consistent with use in protective coating compositions.

It is apparent that dimorphccolic acid, the methyl ester of dimorphccolic acid, and the methyl ester of all-trans- 8,10,12-octadecatrienoic acid all have utility as intermediates for the preparation of valuable film-forming drying oils. For example, the methyl ester of al1-trans-8,10,12- octadecadienoic acid could be trans-esterified with penaerythritol to provide an excellent drying oil.

The following specific examples further illustrate the practice of our invention.

Example 1 Coarsely crushed seeds of Dimorphotheca aurantiaca were extracted with petroleum ether in a Soxhlet extractor. The extracted glyceride oil was freed of solvent by evaporation and a 1.3 g. portion of the oil, at least half of the fatty acid content of which consisted of dimorphecolic acid, was saponified by stirring for 3 hours at room temperature with v0.8 N ethanolic KOH. Water was added to the mixture and the unsaponifiables were removed by extraction with ethyl ether. The aqueousalcoholic solution was made just acid to litmus with sulfuric acid, thus freeing the fatty acids from their soaps. The free fatty acids were promptly extracted with 3-4 portions of ether. After drying the pooled ether extracts over sodium sulfate and evaporating the ether, 1.0 g. of free fatty acids remained. These were then dissolved in 10 ml. of acetonitrile saturated with hexane. The above solution was then extracted with five l0-ml. portions of hexane saturated with acetonitrile. The acetonitrile layer was evaporated, leaving dimorphccolic acid as a yellowish semisolid material (-85 percent of theoretical yield, and having a specific UV absorbency value in ethanol of 1020 at 230 m Example 2 A 27.9 g. portion of Dimorphotheca oil obtained by petroleum ether extraction as in Example 1 was transesterified by refluxing for 2 hours in 200 ml. of methanolic sodium hydroxide (prepared by dissolving 4.0 g. of sodium per liter of methanol). The mixture was then acidified by the dropwise addition of acetic acid and diluted with 400 ml. of water. The methyl esters were extracted with 4 successive portions of diethyl ether. The extracts were pooled, dried over sodium sulfate, and evaporated to give 22 g. of the mixed methyl esters. A 3.4 g. portion of the mixed esters was subjected to countercurrent distribution in a 30 tube Craig-Post apparatus, using a 1:1 acetonitrile-hexane system. Methyl dimorphecolate (2.1 gm.) was obtained by pooling and evaporating the contents of tubes 3 to 12, and was found to have a neutral equivalent of 305 (calculated 310) and an infrared maximum at 2.9 indicating the presence of hydroxyl.

Example 3 Dimorphotheca oil (1.096 g.) was refluxed with 50 ml. glacial acetic acid under nitrogen for 1 /2 hours. The solution Was then withdrawn, diluted with water, extracted 4 times with petroleum ether, dried over sodium sulfate, and evaporated to yield a yellow oil whose ultraviolet spectrum in isooctane gave an E value of 1045 at 268 m indicating about 50 percent of conjugated triene. This represents essentially 100 percent conversion of the conjugated hydroxydiene originally present.

Example 4 Dimorphotheca oil (1.007 g.) was refluxed under nitrogen with 0.1 g. of p-toluenesulfonic acid monohydrate in 50 ml. of xylene for 1 hour and then treated as in Example 3. Ultraviolet measurements in isooctane at 268 III/1. gave an E value of 701. This indicated 67 percent conversion of conjugated diene to triene; the latter was present in the product to the extent of 32 percent.

Example 5 Dimorp'notheca oil (1.07 g.) was refluxed with 5 ml. of 0.25 N methanolic hydrochloric acid under nitrogen for 2 hours forming the methyl ester of all-trans-8,l0,12- octadecatrienoic acid. The product was treated as in Example 3 and the ultraviolet spectrum in isooctane determined. The maximum at 268 m showed the E value to be 990. Essentially quantitative conversion of diene to triene was indicated.

Having fully disclosed our invention, we claim:

1. A method of obtaining 9-hydroxy-trans,trans-10,12- octadecadienoic acid comprising extracting the seeds of a glyceride-containing species of the genus Dimorphotheca with a solvent for the glycerides to remove the glycerides therefrom, evaporating the solvent, saponifying the glycerides to form a mixture of the alkali metal soaps, of the fatty acids, including that of 9-hydroxy-trans,trans- 10,12-octadecadienoic acid, acidifying to free the acids from the alkali metal soaps, and separating the 9-hydroxytrans,trans-10,12-octadecadienoic acid from the mixture.

2. The method of claim 1 wherein the solvent for the glycerides is petroleum ether.

3. The method of claim 1 wherein the solvent for the glycerides is petroleum ether and wherein the separation of the 9-hydroxy-trans,trans-10,12-octadecadienoic acid from its mixture with other fatty acids is effected by form ing a mixture of all these fatty acids in acetonitrile saturated with hexane and extracting this acetonitrile-hexanefatty acid mixture with a mixture of hexane saturated 5 with acetonitrile.

4. A method of preparing a lower alkyl ester of 9- hydroxy-trans,trans-10,12-octadecadienoic acid comprising extracting the seeds of a glyceride-containing species of the genus Dimorphotheca with a solvent for the glycerides to remove the glycerides therefrom, evaporating the solvent, reacting the glycerides with a lower alkanol in the presence of a non-acidic esterification catalyst to form a mixture of lower alkyl esters of fatty acids including the corresponding lower alkyl ester of 9-hydroxy-10, 12-trans,trans-octadecadienoic acid, and separating the said lower alkyl ester of 9-hydroxy-10,12-trans,trans-octadecadienoic acid from the mixture.

5. The method of claim 4 wherein the solvent of the glycerides is petroleum ether.

6. The method of claim 4 wherein the alkanol is methanol.

7. The method of claim 4 wherein the separation of the lower alkyl ester of 9-hydroxy-10,12-trans,trans-octadecadienoic acid from its mixture with the lower alkyl esters of the other constituent fatty acids is effected by countercurrent distribution in an acetonitrile-hexane system.

8. The method of claim 4 wherein the solvent of the glycerides is petroleum ether, the alkanol is methanol, the esterification catalyst is sodium methoxide, and the separation of the lower alkyl ester of 9-hydroxy-10,12- trans,trans-octadecadienoic acid from its mixture with the corresponding lower alkyl esters of other fatty acids is efiected by countercurrent distribution in the acetonitrilehexane system.

References Cited in the tile of this patent UNITED STATES PATENTS 17731, line 3 1957 

1. A METHOD OF OBTAINING 9-HYDROXY-TRANS, TRANS-10, 12OCTADECADIENOIC ACID COMPRISING EXTRACTING THE SEEDS OF A GLYCERIDE-CONTAINING SPECIES OF THE GENUS DIMORPHOTHECA WITH A SOLVENT FOR THE GLYCERIDES TO REMOVE THE GLYCERIDES THEREFROM, EVAPORATING THE SOLVENT, SAPONIFYING THE GLYCERIDES TO FORM A MIXTURE OF THE ALKALI METAL SOAPS, OF THE FATTY ACIDS, INCLUDING THAT OF 9-HYDROXY-TRANS, TRANS10, 12-OCTADECADIENOIC ACID, ACIDIFYING TO FREE THE ACIDS FROM THE ALKALI METAL SOAPS, AND SEPARATING THE 9-HYDROXY TRANS, TRANS- 10, 12-OCTADECADIENOIC ACID FROM THE MIXTURE. 